Pages 279-286. The 50-mile-wide impact structure, which lies hidden beneath the bay and coastal sediments, is the largest in the United States. … Our preliminary 40Ar-39Ar step heating measurements suggest that precise Ar ages on these tektites cannot be acquired by total fusion. ↑ La superficie résultante équivaut à celle de la région … These data, together with optical microscopy suggest a complex trapped component … Its age is usually estimated at around 66 Ma (million years ago), … The age of the Chesapeake Bay crater’s very saline groundwater was then determined by extrapolating to its helium-4 composition from the helium-4 compositions of the dated Maryland groundwater, a technique the authors of this investigation admitted was a “large extrapolation” and “far from precise.” The age of the Chesapeake Bay crater’s groundwater determined by this technique was … The Chesapeake Bay crater is an 85 km impact structure formed during the late Eocene, about 35.4 million years ago. Pages 287-300. For example, tektites found in North America most likely originated from the impact that formed the Chesapeake Bay crater in Virginia. ed by documenting the stratigraphic ranges of three groups of microfossils (planktonic fora ; Wittman, A., et … The Chesapeake Bay Program is a unique regional partnership that has led and directed the restoration of the Chesapeake Bay since 1983. The Chesapeake Bay Crater impact site was formed more than 35 million years ago by a comet or asteroid 5 to 8 miles (8 to 13 kilometers) in diameter. Horton, J.W., Jr., and Izett, G.A., Crystalline-rock ejecta and shocked minerals of the Chesapeake Bay impact structure, USGS-NASA Langley Core, Hampton, Virginia, with supplemental constraints on the age of the impact, in Horton et al., Editors, Studies of the Chesapeake Bay Impact Structure—The USGS-NASA Langley Corehole, Hampton, Virginia, and related Coreholes and Geophysical Surveys, USGS Prof. … However, the stratigraphic ranges of key species of … Cross section showing main features of Chesapeake Bay impact crater and three coreholes that provided data on these features. The Chesapeake Bay impact crater is a 56-mile wide, complex peak-ring crater with an inner and outer rim, a relatively flat-floored annular trough, and an inner basin that penetrates the basement to a depth of at least 1.2 miles. The discovery nearly two decades ago of a 90 km-diameter impact crater below the lower Chesapeake Bay has gone unnoted by the general public because to date all published literature on the subject has described it as "buried". The US Geological Survey (USGS) scientists determined that high-salinity groundwater found more than 1,000 meters deep under the Chesapeake Bay is actually remnant water from the Early Cretaceous North Atlantic Sea and is … The Chesapeake Bay impact structure and the North American tektite strewn field 691 wider distribution than outlined above: Harris et al. Preview Buy Chapter 30,44 € Comparisons Between Impactites. The Chesapeake Bay impact crater is one of only a few oceanic impact craters that have been documented worldwide. The Chesapeake Bay crater is of special interest, because it is close to the region identified as the possible source region for the North American tektites, is of about the expected size, and has an age identical to that of the tektites [3]. Preview Buy Chapter 30,44 € Comparisons with Other Impact Craters. Why did so many shallow water wells, especially on the western side of Chesapeake Bay, produce unusually salty water? Chesapeake Bay CraterChesapeake Bay crater is the largestcrater in the U.S. It’s beneath Chesapeake Baythe bay in Virginia. The present freshwater aquifers lie … However, seismic investigations and some "flat" boreholes in which breccias were drilled are not sufficient to confirm initial assumptions. C. Wylie Poag, Christian Koeberl, … The clasts are fragments ripped from previously deposited beds that … The Bay's geology, its present form, and its very location were created by a bolide impact event at the end of the Eocene (about 35.5 million years ago), forming the Chesapeake Bay impact crater and much later the Susquehanna River valley. When the crater wasformed around 35 million years ago, it was theend of the ice age and sea levels were prettyhigh. The Cretaceous–Paleogene (K–Pg) boundary, formerly known as the Cretaceous–Tertiary (K-T) boundary, is a geological signature, usually a thin band of rock. (en) C.Wiley Poag, C. Koeberl et W. U. Reimold, The Chesapeake Bay Crater : Geology and geophysics of a late Eocene submarine impact structure, Berlin, Springer-Verlag, 2004 (lire en ligne) Références [modifier | modifier le code] ↑ (en) Earth Impact Databse ↑ Christian Koeberl, Forage dans le plus grand cratère américain, Pour la Science, juillet 2009. Pages 287-300. The presence of the Chesapeake Bay crater also helps to explain a long-standing question about ground-water quality in southeastern Virginia. Comparisons Between Impactites. The inner basin and outer rim of the Chesapeake Bay Crater are outlined in white in this illustration. The water in some wells is in fact This computer simulation illustrates how an asteroid contributed to the formation of the Chesapeake Bay impact crater. It had puzzled geohydrologists, including Cede Cederstrom, for more than fifty years. Remarkably, in 1995 other researchers had pinned the age of a 50-mile-wide crater now buried in the Chesapeake Bay to almost exactly the same time.These two impacts—the two biggest in the past 65 million years, and among the biggest of all time—struck Earth with a sudden double punch that might even have been simultaneous. Pages 343-363. Located in Ghana, the Botsumtwi crater is roughly the same age and possesses similar chemical compositions to that of tektites located in the Ivory Coast and West Africa, as well as microtektites found off the coast of Africa. Today, that 25-mile-wide (40 kilometers) crater is buried half a mile below the rocky basement of Chesapeake Bay — the 200-mile-long (320 km) estuary linking Virginia and Maryland on the East Coast. The impact crater created a long-lasting topographic depression which helped predetermine the course of local rivers and the eventual location of Chesapeake Bay. Preview Buy Chapter 30,44 € Geological Consequences of Chesapeake Bay Impact. No ejecta field is known to be associated with the Montagnais impact. To the contrary, evidence is presented here that the so-called "upland deposits" that blanket ∼5000 km 2 of the U.S. Middle-Atlantic Coastal Plain (M-ACP) display morphologic, … Recently, (U-Th)/He thermochronology of apatite, titanite, and 61 zircon has proven to be another valuable isotopic system for this purpose (e.g., Ukstins Peate et 62 al., 2010; van Soest et … The Chesapeake Bay impact crater is one of only a few oceanic impact craters that have been documented worldwide. Comparisons with Other Impact Craters. Poag, Dr. C. Wylie (et al.) Pages 301-341. Despite the fact that the structure is deeply buried, it is one of the better studied impact craters in the … C. Wylie Poag, Christian Koeberl, Wolf Uwe Reimold. A line tracing of seismic-reflection data, including basement data down to 6.0 seconds two … It is believed that the Chesapeake structure, with its age of 35.3 million years, is one of the most recent large impact crater on earth. Either a comet or asteroid struck the then-coastal … Age of Chesapeake Bay Impact Crater. The cores sampled a sandy rubble bed, which contains hand-size to person-size chunks (clasts) of clay, limestone, and sand. Seismic profiles … Poag, Dr. C. Wylie (et al.) The North American tektite strewn field, a widespread deposit of distal ejecta, is thought to be derived from the Chesapeake Bay impact, perhaps with a small contribution from the Toms Canyon impact. 58 Previous attempts to determine the age of impact structures, such as the Chesapeake Bay 59 crater, have mainly focused on the use of 40Ar/39Ar or U/Pb geochronometers (e.g., Jourdan et 60 al., 2012 and references therein). The inner basin includes a central uplift surrounded by a series of concentric valleys and ridges. Red triangles represent estimates of age for the groundwater in the Chesapeake Bay impact crater sampled at the well near Eyreville, Virginia. Geological Consequences of Chesapeake Bay Impact. (2004) reported two closely spaced … Age of the Chesapeake Bay crater: Current radiometric age determinations for the Chesapeake Bay crater are based on total fusion Ar ages of tektites (distal impact glasses; [7-10]). During the last Ice Age, mile-thick glaciers stretched as far south as Pennsylvania, and the. Cape Charles, a sleepy town located at the mouth of the bay in eastern Virginia, holds the secret to the origins of the Chesapeake Bay region. The target region was on the marine continental shelf at the time of impact, and most of the region is still or again underwater today. While the source craters for the Central European and Ivory Coast tektite strewn fields are known, the source crater of the North American tektites has remained elusive. Approximately 6,300 geoscientists from around the … Most important for present-day inhabitants of the area, the impact disrupted aquifers. (2004) described the presence of shocked quartz from Georgia, USA. Chesapeake Bay crater: Chesapeake Bay crater is centered near the present mouth of Chesapeake Bay in eastern Virginia, U.S.A..